Method for producing nitroalkanes in a microstructured reactor

Abstract

The invention relates to a process for preparing nitroalkanes by reaction of at least one alkane with at least one nitrating agent in the gas phase, wherein the nitration is carried out in a microstructured reaction zone having parallel channels having hydraulic diameters of less than 2.5 mm and a total specific internal surface area of more than 1600 m 2 /m 3 and the alkane and the nitrating agent are conveyed under a pressure of from 1 bar to 20 bar through the reaction zone and reacted at a temperature of from 150° C. to 650° C. and the reaction products are cooled downstream of the reaction zone and discharged and the at least one nitrating agent is introduced over from two to ten introduction points along the reaction zone.

The invention claimed is: 
     
       1. A process comprising preparing nitroalkanes by reaction of at least one alkane with at least one nitrating agent in the gas phase, wherein the nitration is carried out in a microstructured reaction zone having parallel channels having hydraulic diameters of less than 2.5 mm and a total specific internal surface area of more than 1600 m 2 /m 3 , where the alkane and the nitrating agent are conveyed under a pressure of from 1 bar to 20 bar through the reaction zone and reacted at a temperature of from 150° C. to 650° C. and the reaction products are cooled downstream of the reaction zone and discharged and the at least one nitrating agent is introduced over from two to ten introduction points along the reaction zone, wherein the at least one nitrating agent which is introduced via the from two to ten introduction points comprises an oxygen-rich partial mixture comprising a mixture of oxygen and at least one nitrogen oxide. 
     
     
       2. The process according to  claim 1 , wherein the nitration is carried out in the presence of an inert or passivated internal surface of the microstructured reaction zone. 
     
     
       3. The process according to  claim 2 , wherein the internal surface of the microstructured reaction zone is provided with a silicon coating. 
     
     
       4. The process according to  claim 2 , wherein the interior walls of the reaction channels are made of an inert material. 
     
     
       5. The process according to  claim 1 , wherein the wall thickness between two hollow spaces at every place in the microstructured reaction zone is selected so that intrinsic safety in respect of detonative explosions is ensured. 
     
     
       6. The process according to  claim 1 , wherein inert substances are additionally added to the reaction mixture. 
     
     
       7. The process according to  claim 1 , wherein the reaction products are cooled by at least 10° C. in a further microstructured zone after exit from the reaction zone. 
     
     
       8. The process according to  claim 1  comprising preparing nitropropanes by reaction of propane with a nitrating agent at a pressure of from 1 bar to 20 bar and a temperature of from 200° C. to 350° C. 
     
     
       9. The process according to  claim 1  comprising preparing nitroisooctane by reaction of isooctane with a nitrating agent at a pressure of from 1 bar to 20 bar and a temperature of from 200° C. to 350° C. 
     
     
       10. The process according to  claim 4 , wherein the inert material is silicon, silicon carbide or a glass which in respect of inertness has comparable properties to fused silica or borosilicate glass. 
     
     
       11. The process according to  claim 1 , wherein the oxygen-rich partial mixture is a partial mixture comprising predominantly oxygen. 
     
     
       12. The process according to  claim 6 , wherein the inert substances are nitrogen or water. 
     
     
       13. The process according to  claim 7 , wherein the reaction products are cooled by at least 30° C. 
     
     
       14. The process according to  claim 8 , wherein the nitrating agent further comprises nitric acid. 
     
     
       15. The process according to  claim 9 , wherein the nitrating agent further comprises nitric acid.